1. Field of the Invention
The present invention generally relates to a cable reel in which a flexible cable, such as a flat cable, is employed to provide electrical connection between a stationary member and a movable member, and more particularly, to a lock mechanism which allows the stationary member and the movable member to have their relative position properly determined and maintained before the cable reel is assembled onto the steering system of an automobile.
2. Description of Related Art
A cable reel for providing electrical connection between a stationary member and a movable member is used as a connector means for various electrical circuits, such as an air bag circuit, incorporated in the steering system of an automobile. In this application, it is necessary that the cable reel be assembled onto the steering system in such a manner that the movable member is able to rotate from the neutral position of the steering wheel by substantially the same extent in either direction. For this purpose, a certain type of cable reel has been used, which includes a position indicator mechanism for offering guidance to the operation of positioning the stationary and movable members.
Such a conventional positioning mechanism has, for example, the following arrangement. A rotary shaft, with a gear supported thereon, is provided on either the stationary member or the movable member, and an engagement portion, engageable with the gear on the rotary shaft, is provided in the other member. Each time the movable member makes one revolution, one of the teeth of the gear engages with the engagement portion, causing the gear to rotate by a predetermined angle. The neutral position of the movable member relative to the stationary member is established when the movable member is in a prescribed position relative to the stationary member with a particular tooth of the gear being located at a particular position. In order to indicate the neutral position, a mark is provided on a particular tooth of the gear, and on a particular position of the member confronting the gear. Prior to the assembly of the cable reel onto the steering system, the marks are aligned with each other so that the cable reel may be assembled in a state where the movable member is in its neutral position relative to the stationary member.
It is necessary that the movable member be maintained in its neutral position relative to the stationary member until the assembly comprising the movable and stationary members is assembled onto the steering system. A locking means for this purpose is disclosed in U.S. Pat. No. 4,735,573. Here, a locking means comprises a lock member having a clip pin, capable of a snapping action, and a locking projection. The clip pin is snap-fitted into a bore formed in the movable member, and the locking projection is fitted into a recess formed in the stationary member. After assembly onto the steering system has been completed, the lock member is removed.
The lock member is formed of a relatively hard material, such as a plastic, and adapted to be attached to and detached from the cable reel by snapping the clip pin, formed integrally with the lock member, into or out of the bore formed in the movable member. If the force with which the clip pin snaps is increased so as to prevent any inadvertent disengagement of the lock member during conveyance, etc., there is a risk that the removal of the lock member after the completion of the assembly onto the steering system may become difficult. If the lock member is forcibly removed, there is a risk that the clip pin may break into pieces, which pieces may stay in the steering system to generate noise when the automobile is running.